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Vitrification
Vitrification (from Latin vitreum, "glass" via French vitrifier) is the transformation of a substance into a glass,A.K. Varshneya. Fundamentals of inorganic glasses. Sheffield: Society of Glass Technology, 2006. that is to say a non-crystalline amorphous solid. In ceramics it gives impermeability to water.Arthur Dodd & David Murfin. Dictionary of Ceramics; 3rd edition. The Institute of Minerals, 1994. Vitrification is usually achieved by heating materials until they liquidize, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a vitrified solid. Certain chemical reactions also result in glasses. In a wider sense, the embedding of material in a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a stable compound that is suitable for ultimate disposal. In terms of chemistry, vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (atoms, molecules, forming blocks) becomes higher than a certain threshold value.M.I. Ojovan, W.E. Lee. Connectivity and glass transition in disordered oxide systems J. Non-Cryst. Solids, 356, 2534-2540 (2010). Thermal fluctuations break the bonds; therefore, the lower the temperature, the higher the degree of connectivity. Because of that amorphous materials have a characteristic threshold temperature termed glass transition temperature (Tg): below Tg amorphous materials are glassy whereas above Tg they are molten. The most common applications are in the making of pottery, glass, and some types of food, but there are many others, such as the vitrification of an antifreeze-like liquid in cryopreservation. Ceramics Vitrification is the progressive partial fusion of a clay, or of a body, as a result of a firing process. As vitrification proceeds the proportion of glassy bond increases and the apparent porosity of the fired product becomes progressively lower.Arthur Dodd & David Murfin. Dictionary of Ceramics; 3rd edition. The Institute of Minerals, 1994.'Role Of Accessory Minerals On The Vitrification Of Whiteware Compositions.' N.M.Ghoneim; E.H.Sallam; D.M. Ebrahim. Ceram.Int. 16. No.1. 1990. Vitreous bodies have open porosity, and may be either opaque or translucent. In this context 'zero porosity'; may be defined as less than 1% water absorption. However, various standard procedures define the conditions of water absorption. Whitewares: Production, Testing and Quality Control. William Ryan & Charles Radford. Institute of Materials, 1997'Methods Of Extending The Narrow Vitrification Range Of Clays.' E.V. Glass & Ceramics 36, (8), 450, 1979.'Control Of Optimum Vitrification In Vitreous And Porcelain Bodies.' E.Signorini. Ceram.Inf. 26. No.301. 1991 An example is by ASTM, who state "The term vitreous generally signifies less than 0.5 % absorption. except for floor and wall tile and low-voltage electrical insulators which are considered vitreous up to 3 % water absorption."ASTM C242-01. 'Standard Terminology Of Ceramic Whitewares and Related Products'. Glazing alone does not make pottery impermeable to water. Porcelain, bone china and sanitaryware are examples of vitrified pottery, and are impermeable even without glaze. Stoneware may be vitrified or semi-vitrified, the latter type would not be impermeable without glaze.'Body Builders.' J.Ahmed. Asian Ceramics. June 2014Arthur Dodd & David Murfin. Dictionary of Ceramics; 3rd edition. The Institute of Minerals, 1994.'An Introduction To The Technology Of Pottery.' Paul Rado, Institute of Ceramics. 1988. References * *Stefan Lovgren, "Corpses Frozen for Future Rebirth by Arizona Company", March 2005, National Geographic Category:Glass Category:Cryobiology